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Introduction to the research

Basic page | Fri 9 Dec 2011

The Department of Earth and Planetary Sciences undertook Butler Bequest funded fieldwork in the Giralia Range, southeast of Exmouth and along the Pillawarra Plateau north of Kalbarri, 17-30 August 2011. This website documents the findings and discoveries made during this trip.

Targets of this fieldtrip included the uppermost and lower part of the ~150 metres thick Gearle Siltstone (exposed in the Giralia Anticline) and the basal Haycock Marl (in the lower Murchison River area). Both are mid-Cretaceous marine units. The Gearle Siltstone is of latest early Albian age at its base (~108 million years old) and of middle Cenomanian age at its top (~95 million years old). The basal Haycock Marl is probably of latest Cenomanian or earliest Turonian age (~92 million years old).

The fieldtrip was highly successful as it resulted in the discovery of the first turtle remains ever found in the Gearle Siltstone (of middle Cenomanian age) and the discovery of an entirely new vertebrate site, or rather a whole series of sites, in the lower, Albian part of the Gearle. These sites produced bones of elasmosaurs and, in particular, ichthyosaurs as well as teeth and vertebrae of several species of sharks, chimaeroids and bony fish. One find, comprising several bones of the lower jaw of an ichthyosaur, is particularly encouraging as the bone surface preservation is excellent.

Fossil wood bored by shipworms (a bivalve) were found at several locations in the centre of the Giralia Anticline.

A new fieldtrip for next year is already planned with the aim of recovering more material of the ichthyosaur as well as prospecting additional sites where the lower part of the Gearle Siltstone is exposed.